1. Field of the Invention
This invention relates to a biaxially oriented container such as a bottle wherein two kinds of plastics are concentrically injected into a cavity to form a parison, and the parison is stretch-blow molded to obtain a section in the form of a three-layer, which is excellent in heat-resistance and gas barrier properties.
2. Prior Art
Plastics used for biaxially oriented containers include plastics, which have the gas barrier properties but are poor in heat-resistance, such as polyethylene terephthalate, vinyl chloride and vinylidene chloride, and plastics which have the heat-resistance but are poor in gas barrier properties, such as polycarbonate, polystyrene and polypropylene.
In bottles for carbonated drinks and the like, both pressure-resistance and gas barrier properties are regarded as important but for container for accommodating contents require heating when or after the container is filled, it is said that they should have the heat-resistance in addition to the gas barrier properties.
Accordingly, the plastics such as polycarbonate having the heat-resistance are poor in gas barrier properties, and therefore, they are difficult to be used for the packing containers. The polyethylene terephthalate which has the gas barrier properties and can withstand a filling temperature by heat treatment is widely used not only as containers for carbonated drinks but as packing containers for contents which require heating and filling.
However, since there is a limit in gas barrier properties and heat-resistance of polyethylene terephthalate, a means is merely left in which plastics accepted as a container material and plastics having the gas barrier properties or heat-resistance may be formed into a composite in order to obtain a packing container with excellent performances.
The plastics as a container may be formed into a composite by making a sectional composition of wall portions of the container a two-layer or a three-layer. However, in either case, both the gas barrier properties and heat-resistance are not yet enhanced by one layer.